Moratorium

When:

Lookups on Merriam-Webster jumped to the number one spot on May 27, 2010.

Why:

This word figured prominently in President Obama's reaction to the oil spill in the Gulf of Mexico.

For example, as the Associated Press reported,

"The president announced new steps to restrict drilling, including continuing a moratorium on drilling permits
for six months, suspending planned exploratory drilling off the coasts of Alaska and Virginia and ordering a halt to 33
exploratory deep-water rigs in the Gulf of Mexico."  Tom Raum and Jennifer Loven, May 27, 2010

The word moratorium means "a legally authorized period of delay," or "a suspension of an activity."

It comes from the Latin word mora, meaning "delay."

Side note: Another word that comes from this Latin root is remora, the name of the fish (also called a shark
sucker) that attaches itself to large fish and boats. Presumably, the remora got its name from the old belief that the
fish delays its host's progress through the water. Remora can be found in the Gulf of Mexico.